2-element vertical array at oh1nm vert at oh1nm-2.pdf · 2-element vertical array at oh1nm pekka...
TRANSCRIPT
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2-element vertical array at OH1NM
Pekka Ketonen
OH1TV
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The concept
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The goal
•Seaside QTH
•Elevated radials
•Phasing angle 105 degrees
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..the goal
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..the goal
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Step 1
• Measure impedances of the two radiating elements
• Two measurements per element
– Feedpoint impedance, when the other element is open
– Feedpoint impedance, when the other element is closed (short
circuit)
• This measurement is needed for mutual impedance calculations
• See results on next pages
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West element, east element open
This comes from a
near by dipole tuned
to 3650kHz
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West element, east element closed
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East element, west element open
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East element, west element closed
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Step 2
• Calculate mutual impedance. The result shall be about
the same both ways. If there is more than 1 ohm
difference, there must be an error in the measurement or
disturbing other element close by
• Calculate phasing components
• Calculate input impedance of the array
• Calculate L-match components
• Results are shown in the phasing box schematic
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Phasing box, schematicphasing angle 105 degrees
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Step 3
• Build the phasing box, make the 0.5 lamda cable, install
• Measure SWR in both directions
• If the work so far has been done carefully, componets
selected with 2% tolerance, no tuning is needed after
installation.
• See results on next pages
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Array SWR, direction east
This comes from a
near by dipole tuned
to 3650kHz
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Array SWR, direction west